Laser-based sensors that interrogate chemical samples across a range of optical wavelengths often make use of a tunable laser system such as a tunable external cavity laser (ECL). As the laser scans across its wavelength range, the output power of the ECL varies. The output power typically reaches a maximum somewhere in the middle of the scan, and falls to zero on either edge of the scan. In order to compensate for various aspects of the power variation, a separate photodetector can be employed to measure the power output of the laser independent of any absorption signatures. The separate photo detector may be separate from any photo detector involved in the detection process. Absorption spectra derived from the sensor can then be divided by the power spectrum to provide a power-normalized spectrum. Need for an extra photodetector is a limitation of chemical sensors employing power normalization because of the increased size, weight, and power required. The present invention addresses these and other problems by providing laser configurations and methods that obviate the need for an extra photo detector dedicated specifically to measure power output of the laser (i.e., for power normalization) for chemical sensing applications, thus reducing the size, weight, and power required for such systems. It further provides a method for determining the circulating power of external cavity lasers and for precise and sensitive detection of analytes without the need for a separate detector.